April, 1948
1313
CATALYTIC REDUCTION O F METHYLFURAN TO %PENTANONE
catalyst chamber consisting of a Pyrex glass tube, 1.7 in. diameter, and heated electrically. The metal was activated by oxidation in a stream of air at 500 O followed by slow reduction below 300' with hydrogen. The weight of each catalyst and the amount of water produced at the fust reduction was as follows, pure nickel (2500 g., 250 cc.), pure cobalt (2300 g., 869 cc.), nickel-copper (50% of each, 2500 g., 607 cc.) and cobalt-copper (50% of each, 2500 g., 425 cc.). Copper chromite (750 g.) prepared by the y a l precipitation method was inactive at 225" and 350 The catalysts were reactivated by oxidation and reduction as above. Isolation and Analysis of Products.-Dihydropyran was prepared by dehydration of, tetrahydrofurfuryl alcohol over aluminum silicate at 350 After drying over solid sodium hydroxide it had b. p. fS6-88". The product issuing from the catalytic chamber containing the active metals was passed through a trap a t -78" and the condensed portion distilled at atmospheric pressure. Material, b. p. below 20", consisted of Cdhydrocarbons. Bromine was added at -78" until addition was complete and the volatile unreacted butane distilled off into a graduated tube where its volume a t 0" was measured. The involatile bromide was weighed and the amount of butene to which it corresponded was calculated. The bromide had b. p. 159-160" and would therefore appear to consist essentially of the symmetrical butene dibromide. Theoboiling point of the 1,2-compound is recorded as 166 The fraction of the products collected !etween 20 and 100" boiled mainly between 70 and 90 It appeared to contain only di- and tetra-hydropyrans in addition to a little water. The organic substances were estimated in one of three ways depending on the accuracy desired, each method being checked using authentic mixtures. The most accurate was to weigh the precipitated Shydroxyvaleraldehyde 2,4-dinitrophenylhydrazone formed by adding a weighed sample to excess of a saturated solution of the hydrazine in hydrochloric acid (2 N ) ; the accuracy was 1% with a mixture of equal amounts of the pyrans. A second method, accurate to 6y0with the same mixture of pyrans, was to measure the reduction in weight of a sample (5 cc.) after shaking with hydrochloric acid (2 N ) saturated with sodium chloride. Shaking and separation were carried out in a micro-separatory funnel. This method was only reliable when the pyrans were present in approximately equal amounts. The third method
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[CONTRIBUTION FROM
THE
depended on titration of a sample with bromine (about M ) dissolved in aqueous acetic acid (50%) containing sodium acetate (5%). The last method was the most rapid but least reliable. Cyclopenotanone was estimated in the material, b. p. above 100 , by measuring the reduction in weight after shaking with excess of saturated sodium bisulfite. The method was accurate to within 5% of the ketone which usually amounted to about half the material. A more accurate method for small quantities depended on precipitation with dinitrophenylhydrazine. In the experiments with nickel, distillation of the material from the last fraction and insoluble in bisulfite gave a small quantity, b. p. 136-142", which may have been cyclopentanol. It could not be induced to give a solid dinitrobenzoate and was therefore unidentified. Experiments with cobalt-copper were Carrie: out over Cyclo; a range of temperatures between 200 and 350 pentanone was formed in all the experiments above 250 in amounts similar to those with the cobalt catalyst. Reduction and fission were also observed and the catalyst deteriorated in use. The nickel-copper catalyst was investigated only at one temperature (275"). Dihydropyran (84 9.) was passed over the catalyst with hydrogen (24 l./hr.) during tw: hours. The product contained n-butane, b. p. 0-2 (6 g.), tetrahydropyran, b. p. 87-89' (44 g.), and cyclopentanone, b. p. 129.5-130_5" (7.5 g.), 2,44initrophenylhydrazone, m. p. 14S143 , m. m. p. with an authentic specimen (m. p. 144145") was 142-143'. There was no unsaturated material.
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Summary 2,3-Dihydropyran has been shown to undergo three simultaneous reactions when passed with hydrogen over catalysts containing nickel or cobalt a t a temperature of 200' or above. The reactions are (1) reduction to tetrahydropyran, (2) fission to butene, butane and carbon monoxide and (3) rearrangement into cyclopentanone. The mechanism of the reactions is discussed. KOTREDAME,INDIANA
DEPARTMENT O F CHEMISTRY, UNIVERSITY
OF
RECEIVED AUGUST18, 1947
NOTREDAME]
Reactions of Furan Compounds. X. Catalytic Reduction of Methylfuran to 2Pentanone BY CHRISTOPHER L. WILSON Reference was made some years ago1 to the formation of small amounts of 2-pentanone (11) and 2-pentanol (111) during the gas phase reduction of methylfuran (I) to tetrahydromethylfuran (IV). Experiment has now shown that either tetrahydromethylfuran or 2-pentanone can be the major product depending on conditions. Results obtained using a nickel catalyst at various temperatures are shown in the diagram. At 100' the chief product (86% yield) was tetrahydromethylfuran but as the temperature was raised the quantity decreased and ketone appeared in increasing amounts attaining a maximum (yield 75%) a t about 185'. Along with the ketone a small quan(1) French Patent 811,695 (1937).
tity of its reduction product, 2-pentanol, was also formed. Below 150' conversion of methylfuran was complete but surprisingly enough a proportion escaped reaction above this temperature. This coincided with the formation of quantities of gaseous products, with a slight increase in the amount of tetrahydromethylfuran and with a rapid drop in ketone production. No adequate explanation of these variations has yet been found but the reason is undoubtedly connected with complex surface conditions. Furthermore, nuclear hydrogenation of methylfuran might be reversible. Other metallic catalysts such as cobalt and mixtures of nickel, cobalt or iron with copper as well as copper chromite also gave some ketone but a
CHRISTOPHER L. WILSON
1314
detailed study of their behavior has not been made.
30 &
d 8 20 3 a* 10
200 308 Temperature. Fig. 1.-Products from methylfuran and hydrogen over a nickel catalyst at various temperatures. Each point corresponds with the passage of 41 g. of methylfuran and SO liters of hydrogen over the catalyst in two hours. 100
At present there is little information from which to propose a reaction mechanism. It is particularly uncertain to identify the chemical steps of a catalytic reaction by duplicated experiments with possible intermediates since the conditions on the surface are no longer comparable. Experiment has shown that tetrahydromethylfuran on passage over the catalyst with hydrogen below 200' does not give any ketone. If we ignore the criticism just made of this type of experiment, this fact indicates that ring fission must occur before ring saturation. It may occur therefore either in methylfuran itself or a derived dihydro- compound.
I
-
v
has been presented before3p4to account for the formation of some y-acetopropyl alcohol (VI) during the catalytic reduction of methylfuran in the presence of dilute acid. Presumably dilute acid would hydrolyze 4,5-dihydromethylfuran to acetopropyl alcohol just as it converts 2,3-dihydrofuran into y-hydroxybutaldehyde.2 There still remains the possibility, however, that ring fission occurs in methylfuran itself in the vapor phase by reduction, although the absence of unsaturated products would appear to discount it, and in the experiments in aqueous acid by hydrolysis followed by reduction. In connection with the last point it was shown in the present work during attempts to devise a method for estimating methylfuran that it reacted in the cold with a solution of dinitrophenylhydrazine in dilute hydrochloric acid to give levulinic aldehyde bis-dinitrophenylhydrazone (VII) An analogous reaction is the formation of the dimethylacetal by reaction with methyl alcoholic hydrogen ~hloride.~ Levulinic aldehyde might then reduce further to acetopropyl alcohol. It will be recalled2that the reaction of tetrahydrofurfuryl alcohol vapor with a nickel catalyst gave rise to many products including some 2-pentanone. The present work confirms the view then expressed that the ketone arose by fission of methylfuran which was formed from furfuryl alcohol present as an impurity in the commercial tetrahydro-alcohol.
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Experimental Materials.-Methylfuran, b. p. 63-64', was prepared by reduction of, furfuraldehyde using a copper chromite catalyst at 275 The feed rate was 48 cc. of furfural and 45 liters of hydrogen per hour. The product was distilled, dried over sodium hydroxide and redistilled. Catalysts.-The description of these excepting ironcopper and pure copper was given in the preceding paper. Iron-copper sintered powder (4% copper, 2200 g., 4-16 mesh) was oxidized at 550 and reduced below 400 " giving
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IV
\
JHaO+ Hz/Ni
\
JHsO+ H*/Ni CHaCOCH2CHzCHO CH*COCHzCHzCHzOH 7 (dinitrophenylhydrazone) VI1 VI
In Part I11 of this series2evidence was presented showing that 2,3-dihydrofuran was much more to hydrogenative ring fission than either furan or tetrahydrofuran and that the carbon-oxvnen bond remote from the carbon double bond G& the more readily attacked. Applying these ideas to the reduction of methylfuran would the intermediate formation of an unindicate .~~ _. . stable 4,5-&hydromethylfun (V) . Evidence for the formation Of this (2) Wilson, J . Chcm. Soc., 54 (1945).
Vol. 70
CHaCOCHzCHzCHa I1
J.
CHsCH(OH)CH2CH2CHs I11
64 cc. of water. The pure copper contact material was produced by reducing the granular oxide (1840 g.) below 200'. This metal t i l e d to have any effect on methylfuran On the other hand, copper chromite either a t 280 or 320 eave a 52% vield of 2-ventanone a t 340' together with a k t l e pentan61. Cobalt-copper gave rise to rather more low-boiling materials. The yield of ketone was about 60% at 350". Iron-copper a t 350" gave ketone (4.0 g.), tetrahydro-
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(3) Topchiev, Comgl. rend. Acad. Sci., U. R. S. S.,19,497 (1938):
corn pound and Von RorB, THISJ ' o n a ~ n69,872 ~, (194,). ( 5 ) Harries, Be?., 81, 41 (1898).
April, 1948
ALKYLATION METHOD OF CONVERSION OF KETONES TO PRIMARY AMINES
methylfuran (10.8 g.) and unchanged methylfuran (18.1 g.) from an input of 41 g. Isolation and Analysis of Products.-The product: from the reaction chamber were caught in a trap a t -78 and freed from water either by filtering with exclusion of atmospheric moisture through a small sintered glass funnel kept very cold or by using anhydrous magnesium sulfate. Distillation was effected a t atmospheric pressure with a 12-plate fractionating column. Methylfuran constituted most of the fraction, b. p. 60-70". The amount was checked by conversion into the maleic anhydride adduct using benzene as solvent. Tetrahydromethylfuran was present in the fraction b. p. 70-90" (most 7980') ; 2-pentanone distilled mainly between 101 8ft.d 103", the fraction being collected between 90 and 110 This fraction was shaken with saturated aqueous bisuEte and correction applied for the small amount of non-ketonic material. The distillation residue contained 2-pentanol, usually too little for separation by distillation. The material from several experiments was collected, any ketone removed by bisulfite and the materialthown by distillation to contain 80% of b. p. 117-120 The figures for 2-pentanol are perhaps the least accurate of those recorded. The 2,4-dinitrophenylhydrazone of 2-pentanone a f t y recrystallization from ethyl alcohol had m. p. 146-147 The 3,5-dinitrobenzoate of 2-pentanol roecrystallized from ligroin, b. p. 90-120', had m. p. 61-82 Reduction of 2-Pentanone.-The ketone (15 g.) was passed with hydrogen (15 1 . 4 . ) during thirty minutes The product consisted over the nickel catalyst a t 100 of unchanged pentanone (20 g.) and 2-pentanol (12.3 g.). Dehydrogenation of 2-Pentanol.-The alcohol (10 g.) was passed over the nickel catalyst a t 225" together with hydrogen (30 l./hr.). The product contained 95% ketone. Similar results were obtained at 250 Tetrahydromethylfuran.-The cyclic ether, b. p. 8081" (30 g,), was passed during one hour together with hydrogen (30 l./hr.) over nickel at 250". No ketone was
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produced but there was considerable gas formation. At 100 ' the compound was recovered unchanged. Reaction of Methylfuran with Dinitrophenylhydrazine. -Methylfuran (1 9.) and 2,4dinitrophenyihydrazinedissolved in hydrochloric acid (2 N ) were shaken for several days. The yellow precipitate (1.3 8.) was iiltered off, washed with water and hot ethyl alcohol. I t was insoluble in all ordinary solvents but was crystallized from dimethylformamide forming dark red prisms, m. p. 231" (dec.). Anal. Calcd. for ClrHlsOeNs: C, 44.3; H, 3.5; N, 24.2. Found: C,44.4; H,3.5; N,24.2.
Acknowledgment.-The author is indebted to M. J. While for help with the experiments and to Revertex, Ltd., in whose laboratories some of the work described in this and the preceding three papers in this series was carried out.
Summary The variation of 'products with temperature in the reaction of methylfuran vapor with hydrogen over a nickel catalyst has been studied. At 100' the main product was tetrahydromethylfuran while above this temperature 2-pentanone was formed in large amounts. The yield of ketone was a maximum a t 185'. Along with the ketone small amounts of 2-pentanol were also formed and a t the higher temperatures quantities of gaseous materials. Other catalysts containing cobalt, copper and iron also resulted in ketone formation but a detailed study of their behavior was not made. NOTREDAME,INDIANA
RECEIVED AUGUST18,1947
[CONTRIBUTION FROM THE N O Y E S CHEMICAL LABORATORY, UNIVERSITY OF ILLINOIS]
A Low Pressure Reductive Alkylation Method for the Conversion of Ketones to Primary Amines1 BY ELLIOTR. ALEXANDERAND ALICE LOUISEMISEGADES~ It is well known that carbonyl compounds can be hydrogenated in the presence of ammonia to produce mixtures of primary, secondary, and tertiary amine^.^ Originally the reaction was carried out by the hydrogenation of the carbonyl compound in ethanol, saturated with ammonia, a t low pressure over a nickel catalyst.3a Better yields and more reproducible results, however, have been obtained over Raney nickel with hydrogen pressures of 20 to 150 atmos heres a t temperatures ranging from 40 to 150?8b93C This technique, while readily carried out, requires high pressure apparatus which is not always available. Aecordingly, it was the object of this work to improve Mignonac's low pressure reductive alkyla(1) Taken from a thesis by Alice Louise Misegades submitted t o the faculty of the University of Illinois in partial fulfillment of the requirements for the degree of bachelor of saence. (2) Present address: Albertus Magnus College, New Haven, Connecticut. (3) (a) Mignonac, Corn$;. rend., 179, 223 (1921); (b) Schwoeglu and Adkins, THISJOURNAL-,61, 3499 (1939); (c) Winans, ibid., 61, 3566 (1939).
tion reaction for the preparation of primary amines. It appeared that this might be done by taking advantage of the fact that a primary amine is more basic than ammonia. If ammonium ions were introduced into the reaction mixture, the following reaction should occur in which the position of equilibrium should favor the products on the right. H
'
R-N: I H
+
[fl' [ H:N:H
R-i-H]'+
:T--H H
(1)
Since the alkylammonium ion no longer has an electron pair available for combination with the carbonyl group, the process should tend to stop at the formation of primary amines.
